Effect of average interlayer spacing on capacitance of NiMn layered double hydroxide

The experimental specific capacity of layered double hydroxide electrode is obviously lower than theoretical specific capacity due to its ordinary interlayer spacing. Therefore, getting large interlayer spacing by big size anions intercalation to improve the capacity performance becomes a important research topic. In addition, the quantitative relationship between interlayer spacing and capacitance performance has not been systematically revealed. In this paper, we synthetised and regulated interlayer spacing of NiMn layered double hydroxide from 7.38 to 28.41 angstrom by adding different moles sodium dodecyl sulphate as intercalating agent using one step method, and defined average interlayer spacing to describe more than one interlayer spacing. We found that specific capacity in three-electrode system and capacitance of hybrid capacitor device are positively correlated with the size of the average interlayer spacing in NiMn layered double hydroxide. The sample with the biggest average interlayer spacing of 28.41 angstrom obtains the highest specific capacity of 325, 290, 258, 209 mA h g-1 under 1, 5, 10, 20 A g-1 current density, respectively. The capacitance of hybrid capacitor device assembled with the biggest average interlayer spacing sample as positive electrode acquire the highest capacitance of 131, 82, 60 F g-1 under 1, 5, 10 A g-1, respectively. In addition, the hybrid capacitor device acquire the highest energy density and better cycle stability. What found can help to design the better structure of LDH for good capacitance performance.